To date, processes in which a non-liquid fluid, such as air, is used to convey dry solid additives, such as fibers, for example pulp fibers, for the forming of an article of manufacture, for example a fibrous structure, such as a sanitary tissue product, comprising the pulp fibers, have suffered from a contradiction of high throughput, mechanical complexity, and individualization quality of the dry solid additives, for example lack of agglomerations of the dry solid additives. Existing dry solid additive delivery systems have been designed as a series of unit operations that, while serving their purpose, are not arranged in a holistic manner to address the key transformations required to form a high quality fibrous structure. The present invention describes novel ways to address these contradictions.
The low density and viscosity of typically used non-liquid fluids, such as air (especially when compared with water, another key conveying fluid for the formation of fibrous structures comprising solid additives) have resulted in dry solid additive systems with high mechanical complexity and relatively low throughputs when compared to liquid/wet solid additive delivery systems as used in wet laid papermaking processes. Examples of such mechanically complex dry solid additive delivery systems are shown in Prior Art FIGS. 1A, 1B, 1C, and 1D. These dry solid additive delivery systems show contraptions which aid in the redistribution of dry solid additives introduced to them. These dry solid additive delivery systems are typically fed via a prime mover such as a centrifugal fan. As such, the discharge of the fan is typically round in cross section and thus exhibits an aspect ratio of 1. In order to spread the dry solid additives across a wide length for the forming of fibrous structures, a corrective action, such as a pinned roller or some other method of air and particle redistribution must take place.
Prior Art FIG. 1A illustrates an example of an existing dry solid additive delivery system for delivering individualized dry solid additives. The system comprises a round to square (or high aspect ratio) diffuser. The dry solid additive delivery system is plagued with mechanical complexity by requiring a plurality of rotors, which are cross flow members that rotate during operation to mitigate clumping and/or agglomerating of the dry solid additives passing through the dry solid additive delivery system.
Prior Art FIG. 1B illustrates an example of an existing dry solid additive delivery system in which individualized fibers are fed into a rotating device above a screen, which are both cross flow members. This dry solid additive delivery system still exhibits mechanical complexity as mechanical air foils are used to assist dry solid additives in passing through the system and to prevent the screen from clogging by the dry solid additives.
Prior Art FIG. 1C illustrates an example of an existing dry solid additive delivery system for delivery of individualized dry solid additives. The system utilizes rotating cylinders, which are cross flow members that comprise slot openings to permit the individualized dry solid additives to pass through. The individualized dry solid additives enter into the end of cylinders whose axis of rotation is perpendicular to the direction of a fibrous structure being made from the dry solid additives. The cylinders rotate during operation to mitigate clumping and/or agglomerating of the dry solid additives passing through the dry solid additive delivery system.
Prior Art FIG. 1D illustrates an example of an existing dry solid additive delivery system for delivery of individualized dry solid additives. The system utilizes a plurality of pinned rolls, which are cross flow members, and introduces the individualized dry solid additives in a perpendicular fashion into a large volume containing a myriad of the pinned rolls. The pinned rolls are rotating during operation to mitigate clumping and/or agglomerating of the dry solid additives passing through the dry solid additive delivery system.
The mechanical complexities of the prior art dry solid additive delivery systems described above create various issues that need to be overcome, such as reliability issues, contamination issues, decreased throughput issues and the like.
FIG. 1E illustrates an example of an existing dry solid additive delivery system for delivery of individualized dry solid additives. This system is mechanically simpler than the previous prior art examples shown in Prior Art FIGS. 1A-1D, no cross flow members like those described above, but it too suffers from the previously noted contradiction. The design of its discretizer that supplies the dry solid additives to the system requires that a high pressure air source (a prime mover) impinge upon teeth of its screenless discretizer. In this instance, the source of kinetic energy in the system is that high pressure air source, which serves to propel the subsequently individualized dry solid additives forward in the system. Its prime mover is positioned at the same position in the dry solid additive delivery system as its dry solid additive source (discretizer). This screenless discretizer prevents the dry solid additives from being fully individualized, resulting in poor formation upon forming a fibrous structure.
One problem with existing dry solid additive delivery systems, especially those used in article of manufacture making systems used to make articles of manufacture comprising such dry solid additives rather than dry solid additive delivery systems used merely to transport dry solid additives, such as is used in the cement industry and coal burning industries, is that the existing dry solid additive delivery systems exhibit reliability, contamination, and/or formation issues due to their mechanical complexity and/or formation issues due to their positioning of their dry solid additive source and their prime mover at the same position within the system.
Accordingly, there is a need for an article of manufacture making system comprising a dry solid additive delivery system that mitigates and/or eliminates the problems associated with known dry solid additive delivery systems.